The present invention relates to a constant current device, and more specifically, to a constant current device formed of chalcogenide materials.
Programmable resistive materials based on chalcogenide glass are being explored for use as non-volatile memory elements. By applying an external stimulus, such as different voltages of selected polarities to a chalcogenide glass in the presence of an available metal such as silver, the internal structure of the chalcogenide glass can be modified to produce high or low resistance states.
One specific example of a chalcogenide glass being investigated for memory use is germanium-selenide (GexSe100xe2x88x92x). Typically, the chalcogenide glass has an associated layer for supplying a metal, which becomes incorporated with the glass matrix to change resistance states. As examples, the associated layer may be a layer of silver or a layer of silver-selenide (Ag2Se).
While the current focus is on using chalcogenide glass for memory devices, the inventors have discovered another use for chalcogenide glass, namely, as a constant current device.
In one aspect, the invention provides a two-terminal constant current device formed of a chalcogenide glass material, and its method of formation and operation. The device comprises a metal-containing layer formed adjacent at least one chalcogenide glass layer which is biased into a constant current state. The constant current device maintains a constant current over a range of applied voltages.
In another aspect, the invention provides a constant current device and a method of forming and operating such a device in which at least one layer of silver-selenide is formed between a first germanium-selenide layer and a second germanium-selenide layer. These layers are provided between a first and a second electrode. A bias voltage is applied to the electrodes sufficient to place the device in a constant current state. The constant current device maintains a constant current over a range of applied voltages.
In another aspect, the invention provides a constant current device and a method of forming and operating such a device in which at least one layer of silver-selenide is formed between a first germanium-selenide layer, a layer of silver, and a second germanium-selenide layer. These layers are provided between a first and a second electrode. A bias voltage is applied to the electrodes sufficient to place the device in a constant current state. The constant current device maintains a constant current over a range of applied voltages.
In another aspect, the invention provides a constant current device and a method of forming and operating such a device in which at least one metal-containing layer, such as silver, is formed on a chalcogenide glass layer such as a germanium-selenide layer. A bias voltage is applied to the layers sufficient to place the device in a constant current state. The constant current device maintains a constant current over a range of applied voltages.
In another aspect, the invention provides a constant current device and a method of forming and operating such a device in which at least one metal-containing layer, such as silver-selenide, is formed with a chalcogenide glass layer such as a germanium-selenide layer, and a layer of silver. A bias voltage is applied to these layers sufficient to place the device in a constant current state. The constant current device maintains a constant current over a range of applied voltages.
In another aspect, the invention provides a method of converting a device that has been exhibiting memory behavior comprised of at least one chalcogenide glass layer and a metal-containing layer, for example, of silver or silver-selenide to a constant current device. A bias voltage is applied to the layers sufficient to place the device in a constant current state. The constant current device maintains a constant current over a range of applied voltages.
In another aspect, the invention provides a method of altering the current characteristics of a constant current device formed with at least one chalcogenide glass layer by manipulation of an applied bias voltage.
In another aspect, the invention provides a method of resetting or raising the current characteristics of a constant current device formed with at least one chalcogenide glass layer to a prior state by manipulation of an applied bias voltage.
These and other features and advantages of the invention will be better understood from the following detailed description, which is provided in connection with the accompanying drawings.